B2: GRABAU'S "TRANSITION BEDS" - KEY ELEMENTS IN A RADICAL REVISION OF HELDERBERG STRATIGRAPHy
James R. Ebert and Damon K. Matteson
Earth Sciences Department
SUNY College at Oneonta
Oneonta, New York 13820-4015
Ebertjr@oneonta.edu; Mattesdk@oneonta.edu
INTRODUCTION AND PREVIOUS WORK
The nature of the contact between the Manlius and Coeymans formations is a recurring theme in the literature of the Helderberg Group. In the early twentieth century, Grabau (1906) interpreted the contact as gradational, with a distinctive zone of "transition beds" present between true Manlius and true Coeymans. Grabau's transition beds are best developed in eastern New York in and near the Schoharie Valley and appear to be absent from other areas (Fig. 1).
In succeeding decades, the contact was regarded as a disconformity, with views varying as to the magnitude of hiatus. Goldring (1935, 1943) indicated that as early as 1927, Chadwick saw evidence for some hiatus (see also Chadwick 1944). In central New York, Smith (1929) described the contact of the Jamesville Member of the Manlius Formation with the overlying Coeymans as unconformable. Logie (1933) felt that the erosion was significant with the Elmwood, Clark Reservation and Jamesville members of central New York absent in eastern parts of the state via erosion. Chadwick (1944, p. 152) reported the contact as "irregular, undulating" and concurred with Logie that the absence of the higher members of the Manlius in eastern New York was the result of significant erosion.
Rickard (1962) reinterpreted the Manlius-Coeymans contact as sharp, but conformable in eastern New York. In central New York, he saw the contact as complex with portions of the Coeymans Formation (e.g., Dayville Member) and higher parts of the Manlius (Elmwood, Clark Reservation and Jamesville members) and other members of the Coeymans (Deansboro/Ravena members) inter-tonguing (Fig. 2). Rickard's stratigraphy became the foundation for nearly all succeeding work on the Helderberg Group. The most notable example is Laporte's (1969) reconstruction of depositional environments.
Rickard (1962, p. 105) acknowledged the possibility that a "post-Jamesville" (subCoeymans) disconformity in central New York might extend into the middle of the Coeymans in east-central New York and to either the top or base of the Coeymans in the Hudson Valley. However, he discounted this interpretation based on the absence of an obvious faunal or physical break and the presence of the transition beds at Cherry Valley. Later, Rickard and Zenger (1964, p. 51) reported that "a layer of pebbles and abundant Favocites sp. occupies the position of the Jamesville with Dayville and Deansboro crinoidal limestones with Gypidula coeymanensis below and above" in portions of the Richfield Springs 15' Quadrangle. Whereas this may be viewed as evidence for erosional truncation of the Jamesville below the Coeymans, Rickard and Zenger (1964) retained the interpretation of Rickard (1962) of gradational facies relationships, as did Laporte (1969).
In the 1980's, Goodwin and Anderson published a series of papers outlining and applying their hypothesis of Punctuated Aggradational Cycles (PACs - a type of small scale allostratigraphic cycles) to the Helderberg Group in New York and elsewhere in the Appalachian Basin. Where the Coeymans Formation overlies the Thacher Member of the Manlius Formation, Goodwin and Anderson (1988) interpreted the contact as a minor, cryptic unconformity. They documented the progressive cutting out of more of their PACs from central New York eastward. However, they continued to support coeval relationships between higher parts of the Manlius and the Coeymans formations by correlating P ACs through these units.

B2: Grabau's "Transition Beds" - Key Elements in a Radical Revision of Helderberg Stratigraphy

Schenevus Creek. Note the well developed cut banks on large meanders.

Outcrop of Gilboa Formation
Outcrop of Gilboa Formation with well-developed ball and pillow structures (see Hutchinson, 1977). Opposite is NYSEG power station and dam on Susquehanna River to form Goodyear Lake.

Outcrops of Onondaga Formation.

Discontinuous outcrops of Tristates Group

Outcrop of Kalkberg Formation

Outcrop of Coeymans Formation
Outcrop of Coeymans Formation in contact with Kalkberg Formation. Contact is marked by a silt-rich bed and the Punch Kill Unconformity of Ebert and Matteson (2003). See also description below for STOP 1.

STOP 1. Cherry Valley- Sprout Brook Road, Otsego County Rt. 32
This road cut is the stratigraphically lowest of a series on Sprout Brook Road (Cty. Rt. 32), Rt. 166 and, U.S. Rt. 20 that expose the entire Lower Devonian section that is present in New York State (See Brett and Ver Straeten, 1997). This outcrop corresponds approximately to Rickard's (1962) section number 94, which was measured in nearby Judd's Falls.
The section begins at the north end of the outcrop with approximately 1 meter of the Rondout Formation. The Rondout is abruptly overlain by the Thacher Member of the Manlius Formation. Near the top of the Manlius Formation, the style of bedding becomes thinner (decimeter scale) and intercalations of dark gray to black shale appear. These beds (total thickness = 0.82 m) constitute an erosionally thinned portion of the Green Vedder Member ("thin-bedded upper Thacher" of Rickard (1962)). These dark shale interbeds have yielded the carbonized biota discussed above and in Matteson, Natel and Ebert (1996).
The contact with the overlying Coeymans Formation has traditionally been placed at the appearance of the first, coarse crinoidal bed. This bed overlies the Terrace Mountain Unconformity (13.27 m from base of section). The lower Coeymans (6.03 m thick) comprises interbedded coarse and fine beds which Rickard equated with the Dayville Member. At the top of the Dayville Member, there is a change in the style of bedding to thicker and more irregular beds. The contact is marked by an erosional surface with several centimeters of relief. Sporadic, in situ favocitid corals encrust the contact. Rare, fine grained intraclasts indicate that this surface marks the position where the Elmwood and Clark Reservation members of the Manlius (which overlie the Dayville to the west) have been removed. This is the Howe Cave Unconformity (19.3 m from base of section).
Overlying the Howe Cave Unconformity, thick, irregular to vaguely nodular beds of the upper Coeymans here have been referred to both the Deansboro and the Ravena members of the Coeymans Formation (see Rickard, 1962). This unit continues to the top of the outcrop (26.6 m). Using distinct horizons of chert and beds bearing holdfasts of the cystoid Lepocrinites gebhardi, we have correlated beds from the top of this outcrop with the base of the small outcrop 0.2 miles to the south on Sprout Brook Road. At the latter outcrop, 4.7 m of the Ravena Member is exposed. Thus, the maximum thickness of the Coeymans (Dayville and Ravena combined) is slightly over 19 meters. Previous accounts of the stratigraphy in this area (e.g., Rickard, 1962, 1981; Gurney and Friedman, 1986; Liebe and Grasso, 1990) reported a covered interval between the main outcrop and this smaller exposure and a total thickness of 30 meters for the Coeymans Formation (Rickard, 1981). However, it appears that these authors did not take into account the regional dip, which is approximately two degrees in this area. When relative elevations, the regional dip and the distance between these exposures are utilized, the top of the large outcrop and the base of the smaller exposure coincide. Thus, it appears that previously published measured sections for Cherry Valley have exaggerated the thickness of the Coeymans Formation by as much as 50%. Although we will not visit the smaller exposure on this trip, the Punch Kill Unconformity (Ebert and Matteson, 2003) is well exposed here, where it separates the Coeymans Formation from approximately 2m of the Kalkberg Formation.
Taken together, the Green Vedder beds and the Dayville Member appear to constitute a gradational transition between the Manlius (proper) and Coeymans formations (Rickard, 1962, 1975, 1981). However, such a gradation cannot exist owing to the presence of the regionally traceable Terrace Mountain and Howe Cave unconformities which cap each unit respectively. Furthermore, the upper Thacher (Green Vedder Member) and Dayville Member exposed on Sprout Brook Road correlate to the west with units bearing the same names. They are distinct units and not an ambiguous zone of transition, assignable to neither formation. When correlated westward, they are separated by other members of the Manlius Formation. When traced eastward, these units thin and become the zone that Grabau (1906) designated as transition beds in the Schoharie area. Grabau's (1906) transition beds (sensu strictu) will be seen at STOP 2.

Kalkberg outcrops

Kalkberg outcrops with well-developed K-bentonites
Railroad overpass. Kalkberg outcrops with well-developed K-bentonites (see Smith, Berkheiser and Way, 1986; Ebert, Applebaum and Finlayson,1992; Tucker, et.al., 1998). Kalkberg is disconformably overlain by the Oriskany Sandstone.

Outcrops of Tristates Group
Outcrops of Tristates Group which also bears K-bentonites (see Ver Straeten and Brett, 1997).

Begin outcrop of Onondaga Formation.
Edgecliff, Nedrow and Moorehouse Members are well exposed (see also Brett and Ver Straeten, 1997).

Small outcrop of Seneca Member of the Onondaga Formation.
The Tioga-B (Onondaga Indian Nation) K-bentonite is exposed at the base of the outcrop. This outcrop has provided conodonts which are the subject of direct radiometric dating studies (Research is in progress, but see Elrick, et. al. (2002) for a preliminary report.)

Outcrop of the Marcellus Formation
Outcrop of the Marcellus Formation, including Union Springs, Cherry Valley Limestone and Chittenango members, exposed on Chestnut Street, sub parallel toRt. 20 (see Griffing and Ver Straeten, 1991; also Brett and Ver Straeten 1997).

Outcrops of the Kalkberg Formation at the edge of Leesville.
Exposed section is similar to the outcrop at Cherry Valley (40.0 in this road log).

Outcrops of Kalkberg at edge of Sharon Springs.
Section is similar to Leesville and Cherry Valley.

Outcrop of Onondaga Formation.

Outcrop of Ordovician flysch of the Schenectady/Frankfort Fm.

Note view of Terrace Mountain to the right.

Dunkin' Donuts- a convenient rest stop in this area.

STOP 2: Terrace Mountain Road, Schoharie
In the vicinity of Schoharie, there are numerous outcrops of Grabau's (1906) transition beds. This exposure on Terrace Mountain Road probably postdates Grabau's investigations, however it is one of the most accessible outcrops for examining these beds. Therefore, we selected it for this trip, rather than one of Grabau's "classic" outcrops, many of which still exist.
In this exposure, the two-fold character of Grabau's transition beds is readily apparent. The lowest beds in the outcrop comprise a thinned eastward extension of the Green Vedder Member (Rickard's "thin-bedded upper Thacher"). The Terrace Mountain Unconformity is marked by the abrupt appearance of coarse, crinoidal grainstones and packstones of the Dayville Member of the Coeymans Formation. Note that this is an extension of the term Dayville. In Rickard's (1962) stratigraphy, the Dayville did not extend eastward beyond Cherry Valley. Several of the Dayville beds display well-developed structures associated with tempestites: vertical grading, undulating to hummocky cross stratification and rare symmetrical ripple caps.
The Dayville has been substantially thinned from 6 m at Cherry Valley to approximately 1 m in the Schoharie area. This thinning is a result of the eastward descent of the Howe Cave Unconformity, which separates the Dayville from the overlying Ravena Member of the Coeymans Formation. Minor local relief on the Howe Cave Unconformity is present in the Schoharie region, where the thickness of the Dayville remnant ranges from 0.7 to nearly 1.25 m at various outcrops.
Overlying the Howe Cave Unconformity, thick beds of the Ravena Member of the Coeymans Formation comprise the majority of this outcrop and they extend to the top of the exposed section. Upper portions of the Ravena display abundant club-like holdfasts of the cystoid Lepocrinites gebhardi. We are currently investigating the lateral extent of this subdivision of the Ravena Member (See also Matteson and Ebert, 2001 ).

To the left and uphill, a large outcrop of the Helderberg Group
To the left and uphill, a large outcrop of the Helderberg Group is visible on I-88. This outcrop exposes the Kalkberg, New Scotland and Becraft formations.

The original Lester Howe Hotel and future Cave House Museum.
Also, original entrance to Howe Caverns.

STOP 3: Howe Cave Quarry
The inactive Howe Cave Quarry is the type section of the Howe Cave Unconformity. Clear truncation of the upper transition beds (eastern extension of the Dayville Member) in this quarry enabled recognition of this unconformity within the Coeymans Formation as presently defined. The truncation of beds in the Dayville is best observed in the weathered joint surface on the high wall at the entrance to the quarry, just beyond the old Lester Howe Hotel. In this face, the Green Vedder Member of the Manlius Formation (a.k.a. "thin-bedded upper Thacher") is also readily apparent. The upper part of the high wall is comprised of the massive Ravena Member, which, in parts, bears abundant holdfasts of Lepocrinites gebhardi. Elsewhere in the quarry, the Punch Kill Unconformity is exposed, overlain by approximately one meter of the Kalkberg Formation. This is visible at the top of the high wall in the main part of the quarry, but is only accessible for direct observation in a few places.
Other features of interest in the quarry include a thrust fault (Marshak and Bosworth, 1991; Mylroie and Palmer, 1977), extensive fields of ripples on the floor of the quarry (Ebert, et.al., 2000), numerous glacial striations on the surface above the quarry and, various karst and cave features associated with Howe Caverns and Barytes Cave (Mylroie and Palmer, 1977 and this volume), including the original entrance to Howe Caverns, adjacent to the Lester Howe Hotel.
The Howe Cave Quarry and Lester Howe Hotel will be centerpieces of the future Cave House Museum of Mining and Geology, a scientific and industrial educational facility, which is in the initial stages of development. In addition to various geologic, hydrologic and biologic aspects, the Museum will feature a history of mining and the mining industry, as well as multiple activities in which the public will be able to observe active mining, which is scheduled to resume in parts of the quarry. For additional information on the Cave House Museum, contact the Education Coordinator and member of the Board of Directors, Benson Guenther at the following:
The Cave House Museum of Mining and Geology
P.O. Box220
Cobleskill, New York 12043
E-mail: Cavehouse@cobleskillstone.com